Noise-generating tube



Nov. 26, 1963 R. w. WOLFE ETAL NOISE-GENERATING TUBE Filed July 18, 1960 OUTPUT INVENTOR. ROGER W. WOLFE BY EDWARD J. GROHE JR.

A TTORNE Y United States Patent 3,112,423 7 NOISE-GENERATING TUBE Roger W. Wolfe, South Plainfield, and Edward J. Grohe,

J12, New Brunswick, N.J., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed July 18, 1960, Ser. No. 43,466 3 Claims. 01. SIS-8.6)

fiavorably high level of noise output power with a favor- H ably wide bandwidth.

For purposes of illustration, the principles of the invention are embodied in a magnetron beam switching tube in which the behavior of an electron beam is controlled by crossed electric and magnetic fields. One tube of this type includes an electrode assembly which comprises an elongated central cathode and a plurality of groups of elongated electrodes surrounding the cathode, each group of electrodes including a target or output electrode to which an electron beam flows and from which an output signal is derived, and a spade electrode which forms and holds an electron beam on its target. An external cylindrical magnet surrounds the tube envelope and electrode assembly.

In normal operation of this type of tube as a switching device, a high intensity beam of current flows from the central cathode to a target electrode and is urged to rotate around the tube under the influence of crossed electric and magnetic fields. When this tube is used as a noise generator, the electron beam is held stationary and flows steadily to one or more target electrodes from which the noise signal is obtained. According to the invention, the selected output electrode or electrodes, from which the noise signal is obtained, is coated with a black carbonaceous material which serves to increase both power output and heat dissipation.

The invention is described in greater detail by reference to the drawing, wherein:

FIG. 1 is a perspective view of a magnetron beam switching tube embodying the invention; and

FIG. 2 is a schematic representation of the tube of FIG. 1 and a circuit in which it may be operated.

The present invention relates to magnetron tubes and, particularly, to tubes such as the multi-position type 6700 magnetron beam switching tubes. This type of tube, shown as tube :10 in FIG. 1, is cylindrical in form and includes an envelope I12 which contains a central longitudinally elongated cathode 14 and ten groups of electrodes spaced radially equidistantly from the cathode and surrounding the cathode. Each group of electrodes includes a generally U-shaped elongated spade electrode 16 and a generally L-shaped target electrode 18 is positioned so that each target occupies the spaced between adjacent spade electrodes. Each spade electrode serves to form and hold an electron beam on its corresponding target electrode. A rod-like switching electrode is ordinarily included in each group of electrodes. However, such electrodes are not used in the present invention and are, therefore, not shown. All of the tube electrodes are secured together by means of top and bottom mica disks 22 and 24. The tube 10 also includes means for providing a longitudinal magnetic field therein, for example, a cylindrical hollow magnet 26 surrounding the envelope and providing an axial magnetic field which is utilized in conjunction with electric fields within the tube to control electron beam flow.

According to the invention, the output or target electrodes are specially treated to increase the noise signal output. Thus, the target electrodes are provided with a coating of carbon or carbonaceous material or the like which, preferably, has the dual characteristics of incandescing under electron bombardment and radiating heat. A layer of carbon deposited by means of a Bunsen burner flame is satisfactory. Optimum noise generation is achieved with a thin highly porous, carbon film in which the particles are comparatively distinct and widely spaced. Such a porous layer has a large surface area and high resistance. In effect, such a surface acts like a carbon resistor and the noise produced in such a resistor is proportional to the resistance thereof.

-In operation of the tube 10 as a noise generator, generally an electron beam is not switched from one group of electrodes to the next, but is maintained in a static condition, flowing steadily to one or more output electrodes from which the desired noise signal is obtained. With such an arrangement, only the selected outlet electrode or electrodes which provide the output signal need be coated with carbon.

In FIG. 1, two oppositely disposed target electrodes 18' are shown coated with carbonaceous material. This represents a favorable arrangement since a tube so constructed may be used to provide an output signal from each target. One suitable circuit for operating this tube is shown in FIG. 2 in which the tube 10 is shown schematically with its electrodes arrayed in linear form. The electrode and circuit arrangement are such that a double electron beam is formed and electrons flow from the cathode to two opposed groups of electrodes including the targets 18' which are assumed to be at the 0 and 5 positions or groups of electrodes in tube '10. In the cirouit, the spade electrodes 16 associated with targets 18' are electrically connected by a suitable lead 24. Similarly, the carbon-coated targets [18' at the same positions are connected together by a lead 26 which is coupled through a load resistor 28 both to ground and to a source of positive D.C. potential. An output terminal 60 is also connected to the two targets 18'. All of the other electrodes are electrically connected together in any suitable fashion by leads 32-, 3-4, 36 so that, electrically, they comprise a single unit.

The relative potentials employed with the tube 10 to obtain two electron beams are as follows. The cathode is coupled to a D.C. potential V which is negative with respect to ground; the opposed 0 and 5 spades are coupled to a D.C. potential V which is positive with respect to the cathode; and all other electrodes are coupled to a D.C. potential V which is made highly positive with respect to the cathode. in one operating circuit V was about vol-ts positive, V was about 75 volts negative, V was about volts negative, and V was about 280 vol-ts positive.

:In operation of the circuit of FIG. 2, electrons emitted by the cathode 14 are divided into two beams with one beam flowing to each of the targets =18. To the extent that this type of operation can be compared with current flow to a single output electrode, under similar operating conditions, the present invention provides greater noise output over a wider frequency range.

The presence of the carbon coating on the selected target electrodes improves the power output and heat dissipation within the tube. in operation of the tube 10, the magnitude of the output noise increases with increased 3 current flow from the cathode to the output electrode 01 electrodes. However, as the current increases, the heat generated by the target electrode increases. With the carbon coating, the target electrodes provide a white incandescent light output, and at the same time, the noise signal output is considerably increased. The theory of operation of the invention is that the noise signal includes two components, normal tube noise inherent in the electron beam and carbon resistor noise. The normal tube noise is proportional to the intensity of the beam current which, in this case, may be maintained at a higher-than-usual level because of the heat-dissipating effect of the carbon coating. The carbon resistor noise is proportional to the resistance of the carbon coating which is affected by the thinness thereof and the size and spacing of the particles.

In comparing tubes of the type described with similar tubes of the prior art, it was found that heat dissipation was increased by the present invention from. one watt per target to three watts by means of the carbon coating. Although tubes embodying the invention may be operated under more strenuous operating conditions than similar tubes of the prior art due to the heat radiating carbon coating, and although these conditions cannot be exactly equated, it may be said that tubes embodying the invention provide 100 to 1,000 times more noise over a wider frequency range than the prior art tubes.

What is claimed is:

1. A magnetron noise-generating tube having a cathode and a plurality of groups of electrodes surrounding the cathode; each group including a target electrode which receives an electron beam and produces an output signal therefrom, and a spade electrode which holds an electron beam on its associated target electrode; means providing a longitudinal magnetic field in said envelope; and a heatdissipating noise-generating resistive coating on a selected target electrode, said coating comprising a porous layer of a carbonaceous material having large surface area and comparatively high resistance whereby the dual effects of high heat dissipation and high noise generation are achieved, the tube thus providing noise output including one component of normal electron beam current noise and another component of carbon resistor noise.

2. A magnetron noise-generating tube having a cathode and a plurality of groups of electrodes surrounding the cathode; each group including a target electrode which receives an electron beam and produces an output signal therefrom, and a spade electrode which holds an electron beam on its associated target electrode; means providing a longitudinal magnetic field in said envelope; and a heatdissipating coating on a pair of oppositely disposed target electrodes, said coating comprising a porous layer of a carbonaceous material having large surface area and comparatively high resistance whereby the dual effects of high heat dissipation and high noise generation are achieved, the tube thus providing noise output including one component of normal electron beam current noise and another component of carbon resistor noise.

3. A magnetron noise-generating tube having a cathode and a plurality of groups of electrodes surrounding the cathode; each group including a target electrode which receives an electron beam and produces an output signal therefrom, and a spade electrode which holds an electron beam on its associated target electrode; means providing a longitudinal magnetic field in said envelope; and a heatdissipating coating on a selected target electrode, said coating comprising a porous multi-particle layer of a carbonaceous material the particles of which provide a large surface area and resultant favorable heat dissipation, the porosity of said layer imparting comparatively high resistance thereto whereby improved noise generation results, the tube thus providing noise output including one component of normal electron beam current noise and another component of carbon resistor noise.

References Cited in the file of this patent UNITED STATES PATENTS 2,075,855 Kilgore Apr. 6, 1937 2,146,098 Van Gessel et a1. Feb. 7, 1939 2,848,646 Fan et al Aug. 19, 1958 2,876,381 Moss Mar. 3, 1959 

1. A MAGNETRON NOISE-GENERATING TUBE HAVING A CATHODE AND A PLURALITY OF GROUPS OF ELECTRODES SURROUNDING THE CATHODE; EACH GROUP INCLUDING A TARGET ELECTRODE WHICH RECEIVES AN ELECTRON BEAM AND PRODUCES AN OUTPUT SIGNAL THEREFROM, AND A SPADE ELECTRODE WHICH HOLDS AN ELECTRON BEAM ON ITS ASSOCIATED TARGET ELECTRODE; MEANS PROVIDING A LONGITUDINAL MAGNETIC FIELD IN SAID ENVELOPE; AND A HEATDISSIPATING NOISE-GENERATING RESISTIVE COATING ON A SELECTED TARGET ELECTRODE, SAID COATING COMPRISING A POROUS LAYER OF A CARBONACEOUS MATERIAL HAVING LARGE SURFACE AREA AND 